Controlling weed growth in agricultural fields is an important part of crop production. Weeds compete with crop plants and have the potential to reduce crop yields. Conventionally, farmers use herbicides as one of the primary tools for controlling weeds. In the past, herbicides have worked well in eliminating the tedious job of repeatedly removing weeds through mechanical cultivation. There is, however, a growing concern today that some weeds are developing a resistance to herbicides. These herbicide resistant weeds have created a major management challenge for conventional growers who are increasingly required to resort to new chemicals, mixtures of several chemical herbicides, or mechanical cultivation methods to control such weeds. Moreover, growers who wish to market their crops in the organic food markets (“organic farmers”) are restricted from using conventional herbicides and generally must rely on mechanical cultivation methods.
Presently, several types of mechanical cultivators are available for managing weeds in cases where chemical herbicides are not used including: rotary hoes, tine cultivators, burners fueled by liquid petroleum, and cultivators that use a broad shoe dragged through the soil to cover smaller weeds with dirt and restrict their growth (often referred to as Buffalo cultivators). Each of these cultivation tools is commonly used at a particular stage of the crop (e.g., crop height). After the crop stage has passed, or if the weeds are taller than expected, the effectiveness of any particular cultivation tool is significantly decreased. For example, when excessive rain delays weeding cultivation, the weeds can grow to a size where the cultivation tool that matches the stage of the crop growth can no longer effectively remove the weeds.
Typical agricultural row crop fields, such as those planted with corn or soybeans, are planted with a repeated pattern of rows, each row containing a plurality of individual plants spaced in close proximity to one another, so as to be planted at relatively high density along the row, on average from five to seven inches apart for corn. Row spacing can vary from farm-to-farm, but row spacing is often less than thirty-six inches wide (i.e., crops planted on thirty-six inch centers); for example, rows of corn are often spaced twenty or thirty inches apart.
In general, weeds found in the gaps between rows (between-row weeds) can be managed by making multiple passes over the field with conventional mechanical cultivators, provided that the farmer is able to operate the equipment at the appropriate time in order to prevent weed growth from progressing to the stage where it cannot be managed with available equipment.
Weeds that grow between crop plants within a row (in-row weeds) are difficult to manage effectively. Early in the growing season, an implement such as a rotary hoe can be used to disrupt both between-row and in-row weeds without apparent damage to the crop plants. If the weeds between crop plants end up being considerably shorter than the crop plants when the crop plants are sturdy and approximately 10 inches or taller, then an implement such as a Buffalo cultivator (Bison Industries, Inc.) can be used to pile dirt up in a ridge centered on the crop plant stems, which generally results in the in-row weeds being buried. Similarly, propane flamers (e.g., Flame Engineering, Inc.) can be used to slow or stop weed growth, both between rows and in the area next to crop plants, apparently without significant damage to the crop plants themselves. Finger weeding tools (e.g., Buddingh Weeder Co.) can be used to push soil in between crop plants in order to disrupt weed growth in this area, although good alignment of the tools on the crop row is critical; alignment may be improved with machine-vision solutions to adjust the implement's track side-to-side such that it stays centered on the row (e.g., Einboeck).
There are emerging technologies for weed management that use machine vision to target specific actions. Technologies have been demonstrated whereby a chemical, including concentrated fertilizer or herbicide, is sprayed in a targeted fashion on weeds (Blue River Technology, SwarmFarm); such technologies are applicable to both between-row and in-row weeds. These technologies require reliable weed detection using machine vision and accurate actuation and targeting of the spray. Technical constraints will dictate a minimum cycle time necessary for the full process of weed detection and deployment of the targeted spray. These technical constraints will dictate the forward ground speeds that are possible for effective weed removal. The ground speed of the device will be a key cost driver of such a technology on a per area basis.
While speed of action is required for these smart spraying technologies, actuation is limited to a solenoid valve or the like controlling a spray nozzle. A device that uses a mechanical action of a tool to physically disrupt or remove in-row weeds introduces additional constraints. Like the technologies that detect a weed and spray, these mechanical systems require a minimum cycle time for detection of the weed and removal or disruption by the mechanical device. Importantly, these systems are required to work around and not damage the crop plants. In addition, these mechanical systems have to make good soil contact over what might be rough terrain.
In one example of a mechanical technology, a robotic machine locates weeds with machine vision and then uses a blunt tool to push weeds into the ground (Bosch's Deep Field Robotics). Other technologies have been developed to reach in between crop plants in the crop row while the implement moves parallel to the crop rows (e.g., Robocrop InRow Weeder by Garford Farm Machinery). The required mechanical action must be very rapid and well-guided based on machine vision in order for the overall implement to be able to maintain an economically-relevant forward motion. As crop plant spacing is reduced, in general, the forward speed of such a machine would also need to be reduced. Thus, for a relatively closely-spaced crop like corn, the forward speed may prove too slow to be economical.
According to conventional practices, tractors and implements drawn by the tractors are commonly operated such that their wheels travel within the unplanted space or gap between rows. In this way, the wheels move parallel to the rows as the tractor and implement traverses the field, thereby limiting crop damage. In infrequent cases, farmers operate their equipment perpendicular to rows, for example to apply herbicide. This practice, however, is infrequent as it may cause damage to the crop as the wheels or tires of the equipment drive over the individual plants.
In-row weeds are difficult to remove using conventional equipment, especially on the fields of organic farmers who have restrictions related to chemical use. In-row weed removal is challenging given that current machinery travels within the row, requiring quick action of mechanical weed removal tools in order for technologies to be economical. Further, in-row travel limits the perspective a machine vision system has on the crop rows. In contrast, a machine vision system that moved perpendicular to the row might be helpful to distinguish crop plants from in-row weeds because it would provide a view of crop rows from a generally traverse angle to the row rather than from above the row while moving parallel to the rows. Similarly, a weeding tool that moves generally traverse to the row would have a longer cycle time for sensing weeds and carrying out a mechanical action to disrupt or remove the in-row weeds. In addition, a mechanical weed removal tool might be required to travel a shorter distance to achieve the removal of in-row weeds.
Recently there has been an interest in the use of robotic vehicles that can navigate between planted crop rows on the uneven terrain in the gap between parallel rows of an agricultural field to accomplish in-season management tasks, such as selectively applying fertilizer, herbicides or other agricultural chemicals when the use of conventional tractor-drawn equipment or high clearance machines is no longer feasible. An example agricultural robotic vehicle of this type is disclosed in U.S. Pat. Nos. 9,288,938; 9,265,187, and U.S. Patent Publ. No. 2015/0051779, all of which are incorporated by reference herein. While such a robotic platform provides new ways to perform field work when conventional machines are challenged, they are still designed to travel parallel to the crop rows.
Thus, despite the various weed control measures available, weed cultivation continues to be a problem. In particular, early in the season it has proven difficult to remove weeds that are found within the crop rows between the individual plants. Accordingly, what is needed in the industry is a highly-reliable, cost-effective mechanical weeding system that can effectively remove in-row weeds, as well as between-row weeds. In particular, what is needed is a mechanical weeding platform configured to traverse a field and cultivate weeds generally traverse to the rows of individual plants without causing damage to the crops.